You don’t need a personal trainer if you’re working on a film with George Clooney! The actor directs and stars in the upcoming film The Monuments Men, and recently revealed the prank he played on co-star Matt Damon.

With Matt struggling to lose weight on-set, George took matters into his own hands, by having the wardrobe crew take in his costume everyday, so even if the 42-year-old actor did shed some pounds, it would take him some time to know it.

The film, due out in December, tells the story of art historians and museum curators who are in a race against time to recover renowned works of art stolen by Nazis before Hitler destroys them. And with George’s help, Matt is bound to look pretty damn good in that uniform…